6029. Methyl Bromide

Nomenclature

CAS number: 74-83-9
Bromomethane; monobromomethane; Embafume.
CH3Br; mol wt 94.94.
C 12.65%, H 3.18%, Br 84.16%.

Description and references

Prepd industrially by the action of hydrobromic acid on methanol. Several modifications of the process, e.g., sulfuric acid is added to sodium bromide and methanol, methyl bromide being removed by distillation. Acute toxicity: D. D. Irish et al., J. Ind. Hyg. Toxicol. 22, 218 (1940). Atmospheric emission and potential ozone depletion from biomass burning: S. Man, M. O. Andreae, Science 263, 1255 (1994). Review of toxicology and human exposure: Toxicological Profile for Bromomethane (PB93-110682, 1992) 129 pp.

Properties

Colorless gas. Usually odorless; sweetish, chloroform-like odor at high concns. Burning taste. Non-flammable in air, but burns in oxygen. mp 93.66°; bp 3.56°: Egan, Kemp, J. Am. Chem. Soc. 60, 2097 (1938). Vapor press. (20°): 1420 mm Hg. d40 1.730. d20gas 3.974 g/l; nD20 1.4432. Viscosity (0°): 0.397 cP. Spec. heat at 96.6°: 0.165 cal/g/°C; at 13.0°: 1.97 cal/g/°C; at 25°: 0.107 cal/g/°C. Crit temp 194°. Soly in water (20°, 748 mm): 1.75 g/100 g of soln. Forms a cryst hydrate, CH3Br.20H2O, below 4°. Freely sol in alcohol, chloroform, ether, carbon disulfide, carbon tetrachloride, benzene. LC for rats in air (6 hrs): 514 ppm (Irish).

Caution

Potential symptoms of overexposure by inhalation are irritation of respiratory system; headache; visual disturbance; vertigo; nausea, vomiting, anorexia, abdominal pain; malaise, muscle weakness, incoordination, slurring of speech, staggering gait; hand tremor; convulsions; mental confusion; dyspnea; pulmonary edema; coma; death from respiratory or circulatory collapse. Onset of symptoms may be delayed. Direct contact may cause eye irritation, skin irritation or vesiculation; direct contact with liquid may cause frostbite. Potential occupational carcinogen. See NIOSH Pocket Guide to Chemical Hazards (DHHS/NIOSH 97-140, 1997) p 200; Clinical Toxicology of Commercial Products, R. E. Gosselin et al., Eds. (Williams & Wilkins, Baltimore, 5th ed., 1984) Section III, pp 280-284.

Use

In ionization chambers. For degreasing wool. Extracting oils from nuts, seeds, flowers. Soil or space fumigant for insects, fungi, rodents. Methylating agent. Has been used as fire extinguishing agent.